The rapid ecological degradation and its impact on fish of the Yinyu Island in the Xisha Islands
The degradation of coral reef ecosystem can alter the topographic complexity and biotic composition,thereby affecting the coral reef fish community significantly.Coral reefs in the South China Sea have undergone rapid degradation in recent decades,but the ecological consequences for coral reef fish community remain unclear.The coral reefs of the Xisha Islands have experienced ecological degradation in recent years due to the impacts of high temperature and the outbreak of crown-of-thorns starfish(CoTs).We conducted an ecological investigation on the Yinyu Island of the Xisha Islands,through underwater video transect survey,difference tests and liner regression analysis to assess the ecological degradation of the coral reef and its effect on the coral reef fish community.The results show that:from 2020 to 2021,the live coral cover on the Yinyu Island declined from 33.27%to 9.07%,while the turf algae cover increased from 8.38%to 36.50%.The coral recruitment,species richness and Shannon-Weaner index also decreased from 21.42 ind·m-2 to 3.64 ind·m-2,40.00 to 16.83 and 3.26 to 2.14,respectively.The fish density,species richness,Shannon-Weaner index,declined from 1.77 ind.·m-2 to 1.05 ind.·m-2,30.56 to 17.17 and 2.24 to 1.63,respectively.The biomass of corallivore,carnivore,omnivore and total biomass also declined from 2.45 g·m-2 to 0.43 g·m-2,7.35 g·m-2 to 1.70 g·m-2,7.04 g·m-2 to 0.95 g·m-2,and 32.99 g·m-2 to 11.66 g·m-2,respectively.Within two years,turf algae and macroalgae have dominated the Yinyu Island,but the fish community has not demonstrated top-down control of algae.Among the four functional groups in the whole fish community,the herbivore functional group is the least affected by ecological degradation.The coral species richness constrains the fish species richness and diversity.Based on the results above,we speculate that the rapid degradation of the Yinyu Island is the main reason for the decreased in species diversity,density and the change in the structure of coral reef fish communities.We hope to further increase the frequency and scope of investigations in the future,in order to reveal more deep dynamic relationship between fish communities and coral reef ecological changes.
万方数据
维普
